In the manufacture of commercially used zinc, copper, brass and steel, waste by-products result which include mixtures of metal and metal oxides and other non-metallic ingredients. Such waste by-products are sometimes in the form of drosses, skims and ash produced in the melting and refining of metals. In whatever form, such waste by-products frequently are considered an environmental hazard and require special disposal because many are leachable and can enter ground water systems. Thus, these common waste products frequently cannot be simply dumped for disposal purposes.
In addition, these waste products commonly include metal which have commercial value provided they can be separated economically. Various kinds of separation processes have been developed to recover metal from waste by-products but these generally require multi-step processing that are relatively expensive considering the value of the recovered metals.
In addition, the recovery of zinc from low grade zinc ores, which, after roasting and calcination, basically comprise quantities of zinc oxides, require a high percentage of zinc bearing material for economical recovery of zinc from the ores. These ores would normally require a significant amount of concentrating steps to upgrade the zinc content sufficiently to make recovery of the zinc economically feasible. Complex zinc ores such as zinc silicates and zinc-iron complexes provide even more difficulty in recovery and are therefore usually rejected as suitable zinc ores for conventional practices. Such ores could be used as feed stock for this invention with only minimal preparation.
Hence, the invention herein is concerned with providing an economical, relatively simple process and apparatus for recovering and separating certain metals, particularly zinc and copper, from waste by-products, low grade and certain complex zinc ores which do not respond to standard recovery practices, and the like materials which are normally considered of little value and simultaneously converting what would otherwise be a toxic or hazardous material into non-toxic and commercially useable residue.